bool value query

In SQL, boolean values are often represented as 0 and 1, with 1 representing true and 0 representing false. However, the way you’re trying to convert and compare might be causing the issue.

In your SQL query, you’re trying to use Convert.ToBoolean(tamamlandi) = 1, which is not a valid SQL syntax. Instead, you should directly compare tamamlandi with 1 or true (depending on your database).

Here’s how you can modify your command:

OleDbCommand cmd1 = new OleDbCommand("SELECT tamamlandi, okulno, adisoyadi FROM ogrencigorusme WHERE tamamlandi = true AND okulno = '" + txt_Noara.Text + "'", conn);

Or if tamamlandi is stored as an integer:

OleDbCommand cmd1 = new OleDbCommand("SELECT tamamlandi, okulno, adisoyadi FROM ogrencigorusme WHERE tamamlandi = 1 AND okulno = '" + txt_Noara.Text + "'", conn);

Please replace true or 1 with the correct representation of boolean in your database.

Also, please note that concatenating strings to form SQL queries can lead to SQL injection attacks. Consider using parameterized queries to avoid this. Here’s how you can do it:

OleDbCommand cmd1 = new OleDbCommand("SELECT tamamlandi, okulno, adisoyadi FROM ogrencigorusme WHERE tamamlandi = true AND okulno = ?", conn);
cmd1.Parameters.Add(new OleDbParameter("okulno", txt_Noara.Text));

Again, replace true with the correct representation of boolean in your database. 

Thanks

Hello What is data-type of this column, "tamamlandi",  Could you please run this query on database and share result here,

select tamamlandi,okulno,adisoyadi from ogrencigorusme

I am sorry Jignesh, it was my fault. I have found the error. I had written the textbox name incorrectly..

It gives this error. function convert.toInt32 not defined in expression

OleDbCommand cmd1 = new OleDbCommand("select tamamlandi,okulno,adisoyadi from ogrencigorusme WHERE Convert.ToInt32(tamamlandi) = 1 and okulno = '" + txt_Noara.Text + "'", conn);

 OleDbDataReader dr1 = cmd1.ExecuteReader();

I am sorry to say that I have tried all of them but the result is the same.

Hello Mehmat,

Please use this one,

OleDbCommand cmd1 = new OleDbCommand("SELECT tamamlandi, okulno, adisoyadi FROM ogrencigorusme WHERE tamamlandi = True AND okulno = @OkulNo", conn);
cmd1.Parameters.AddWithValue("@OkulNo", txt_Noara.Text);

OleDbDataReader dr1 = cmd1.ExecuteReader();

OR

OleDbCommand cmd1 = new OleDbCommand("select tamamlandi,okulno,adisoyadi from ogrencigorusme WHERE IIF(amamlandi,1,0) = 1 and okulno = '" + txt_Noara.Text + "'", conn);

 OleDbDataReader dr1 = cmd1.ExecuteReader();

You are using c# function in query which will not support because while executing query SQL server don't know definition of c# convert function. If that is table column you can directly use ColumnName=1. Casting not required